Hydraulic wheel feeding mechanism



March 6, 1934. H. A. SILVEN HYDRAULIC WHEEL FEEDING MECHANISM Patented Mar. 6, 1934 UNITED STATES PATENT OFFICE HYDRAULIC WHEEL FEEDING MECHANISM Herbert A. Silven, Worcester, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts This invention relates to grinding machines, and more particularly to improvements in feeding mechanism for controlling the feeding movement of the grinding wheel.

In the operation of certain types of grinding machines, it is desirable that the feeding mechanism be so arranged as to move the grinding wheel and the work rapidly into close proximity 'and thereafter to permit a relative feeding movement of the work and wheel slowly and with great safety while finishing the grinding operation. After this has been completed, it is desirable to effect a rapid separation of the work and the wheel to permit the removal of the ground work piece and its replacement by a rough blank.

It is the primary object of this invention to provide a feeding mechanism in which a feed screw is utilized for efiecting an adjustment or feeding movement of the grinding wheel, and a 23 fluid pressure system, such as a cylinder and piston, is utilized for bodily moving the feed screw to effect the preliminary and final rapid approaching and separating movements of the wheel and work.

In grinding many types of work, and particularly with a wide-face wheel fed directly and continuously into the work, it is often desirable to move the wheel, first rapidly towards the work and then at a slower rate to grind the work and 30 perhaps at a still slower speed to finish grind it, or to stop the wheel movement altogether. For rapid production methods, the wheel feed should be substantially automatically controlled and the changes in its feed should take place when the wheel has reached certain definite positions. For example, in grinding crankshafts and other similar objects, in which not only the cylindrical portion of the crankpin but also the cheeks and fillets adjacent the end of the crankpin are ground,

it is necessary to move the grinding wheel a considerable distance to position it in proper relation with the object to be ground and also to remove it therefrom to an operative position. In grinding the pin, it is desirable that the grinding wheel be fed as rapidly as possible during the idle movement of the wheel and then to have a slower feeding movement to grind the cheeks and the fillets of the pin and a still slower speed to grind the cylindrical portion or body of the pin and a final stopping of the feed or a removal of the grinding wheel when the work has been reduced to the required size.

It is accordingly one object of this invention to provide a grinding wheel feeding mechanism which is capable of feeding the wheel in a set series of uniform feeds.

It is another object of this invention to provide a simplified control for a wheel feeding mechanism which is so arranged that when the wheel slide has reached a predetermined position, it automatically actuates a mechanism to cause a different but uniform feed thereafter.

It is another object of this invention to provide a fluid pressure mechanism for feeding a wheel slide which is arranged so that the movement of the slide' actuates a throttle valve in the fluid pressure system when the slide has reached a predetermined position to change the feed of the grinding wheel to a different but uniform rate.

It is still another object of this invention to provide a fluid pressure operating mechanism for a grinding wheel slide which permits rapid withdrawal and a rapid approach of the grinding whee. into a position adjacent to the surface of the work; and also to provide a fine precision feeding mechanism independent of the hydraulic system to control or adjust the position of the grinding wheel relative to the hydraulic mechanism.

One embodiment of this invention has been illustrated in the drawings, in which like reference numerals indicate like parts:

Fig. 1 is a cross sectional view through a grinding machine showing the improved wheel feeding mechanism;

Fig. 2 is a fragmentary diagrammatic view of the hydraulic system;

Fig. 3 is a horizontal sectional View on an enlarged scale through the valve taken approximately on the line 3-3 of Fig. 1;

Fig. 4 is a fragmentary vertical section taken approximately on the line 4-4 of Fig. 3, showing the cylinder with the piston in a rearward position and also showing the valve operating mechanism;

Fig. 5 is a similar fragmentary vertical section taken approximately on the line 4-4 of Fig. 3, showing the control lever and the piston in the forward position;

Fig. 6 is a fragmentary sectional view taken approximately on the line 4-4 of Fig. 3, showing the valve in position for positioning the wheel in an extreme rearward position for truing the operative face of the grinding wheel;

Fig. 7 is a fragmentary rear elevation, showing the control lever mechanism for actuating the valve;

Fig. 8 is a fragmentary cross sectional view,

on an enlarged scale; taken approximately on the line 8-8 of Fig. '7;

Fig. 9 is a cross sectional view on an enlarged scale taken approximately on the line 9-9 of Fig. 5;

Fig. 10 is a fragmentary sectional view taken approximately on the line 10-10 of Fig. 8; and

Fig. 11 is a detail view on an enlarged scale of the reversing valve sleeve.

In accordance with one embodiment of this invention, and as illustrated in the drawings, a grinding machine may comprise a grinding wheel 11 rotatably mounted on a wheel slide 12 which is slidably supported on a V-way and flat way on the base 13 of the machine and moved by a cross feed screw. The work piece 14 may be mounted on any of the wellknown work supporting and rotating devices in an operative relation with the grinding wheel. The grinding wheel slide 12 is moved towards and from the work piece to a predetermined position, and preferably as located by a stop, by means of a fluid pressure operated mechanism which is connected to move the cross feed screw bodily endwise, and which is so arranged that the screw may be rotated to eifect a fine adjustment of the position of the wheel. In the preferred construction, the fluid pressure mechanism is so constructed that the wheel may be given a rapid approaching movement to a position adjacent to the surface of the work. and then slowed down to a definite and predetermined speed for rough grinding of the work or stopped, after which a manual feed mechanism may be utilized to produce the grinding feed. The wheel slide 12 is arranged so that it may be fed manually towards and from the work piece when desired. This mechanism may comprise a half nut 15 depending from the wheel slide 12, engaging a feed screw 16 which is rotatably supported in the machine base. The rear end of the screw is supported by an anti-friction bearing 17 and the front end is slidably keyed to a rotatable bushing 18 which is supported in a portion 19 of the base 13. The front end of the sleeve 18 carries a gear 20 formed as an integral part thereof and meshes with a gear 21 on a shaft 22 which is also rotatably supported in the base 13. The front end of the shaft 22 carries a gear 23 meshing with a small gear 24 on a shaft 25 which supports on its outer end a manually operable feed wheel 26. It will be readily apparent from the foregoing disclosure that rotary movement of the hand wheel 26 will transmit a rotary motion to the shaft 25, gear 24, gear 23, shaft 22, gear 21, gear 20 to rotate the sleeve 18 and screw 16 to feed the wheel slide 12 either towards or from the work piece 14, depending on the direction of retation of the hand feed wheel.

To attain the main object of this invention, namely, to provide a rapid movement of the wheel relative to the work, a suitable hydraulic mechanism is provided and is preferably arranged in axial alignment with the feed screw and connected with the end of said screw to move it bodily endwise to produce a rapid movement of the grinding wheel and its supporting slide. As illustrated in the drawings, this mechanism comprises a cylinder 30 having a piston 31 slidably mounted therein. The piston 31 is connected to a piston rod 32 which is pinned to a sleeve 33. The sleeve 33 is slidably mounted in a cylinder 34 in the base 13 and slidably keyed thereto by a pin 35. The sleeve 33 supports the bearing '17 so that any endwise movement of the rod 32 transmits a corresponding endwise movement to the feed screw 16 to move the grinding wheel either towards or from the work.

A fluid pressure system is provided to convey fluid under pressure to either end of the cylinder 30 to produce the desired feeding of the grinding wheel. This system may comprise a reservoir 40 which is preferably mounted in the base of the machine. Fluid passes from the reservoir 40 through a pipe 41 and a gear pump 42 and a pipe 43 to a reversing valve 44 which is arranged to convey fluid to either end of the cylinder 30. Fluid enters the valve 44 through a port 45 into a valve chamber 46 between valve pistons 4'7 and 48. Inthe position illustrated in Figs. 1, 2, and 5, the piston 31 is in its extreme forward position. Fluid under pressure entering the valve chamber 46 passes outwardly through a V-shaped port 49, a pipe 50, through a port 51, into a cylinder chamber 52, to hold the piston with a stop 53 in engagement with an end face 54 of the cylinder.

During the forward movement of the piston 31, that is towards the right (Figs. 2, 4 and 5), fluid is exhausted from a cylinder chamber 56, through a port 57, a passage 58, a pipe 59, through a V- shaped port 60, info a valve chamber 61, through a port 62, and returns through a pipe 63, to the reservoir 40.

In order that the speed of the feeding movement under hydraulic pressure may be controlled to give the desired feeding movement to the grinding wheel, it is desirable to provide a ihrottle valve to regulate the flow of fluid under pressure to or from the hydraulic cylinder. In the preferred construction, a throttle valve 65 is provided in the exhaust pipe line 63 to control the exhaust of fluid from ihe cylinder 30 and thereby control the speed of movement of the grinding wheel. The throttle valve comprises a valve stem 66 having valve pistons 6'7 and 68 arranged to form a valve chamber 69 therebetween. In the positions illustrated in Figs. 2, 3 and 5, fluid passing through a pipe 64 from port 62 enters through a port 70 into the valve chamber 69 and passes out through a V-shaped port '71, through the pipe 63, and returns to the reservoir 40. The V-shaped port '71 is provided to permit a more accurate and delicate control of the feeding mechanism to produce the desired feed of the wheel slide.

The valve 44 is provided with an extending valve slem '75 which is connected by a turnbuckle '76 to a rod '77, having a grooved member '78 mounted on its outer end on the front of the machine base. This valve is preferably manually controlled so that the operator may readily shift the reversing valve to cause either a forward or a rearward movement of the grinding wheel slide. A manually operable lever 79 is pivotally moun ed on a stud 80 which is supported on a bracket 81 on the front of the base 13. In order that the control lever may be moved in the direction it is desired to move the grinding wheel slide, a

double-acting lever is preferably provided. The

lower end of the lever 79 is pro Jided with a yoked poriion 82 which is engaged by an end 83 of a lever 84. The lever 84 is pivoted on a stud 85 and is provided at its lower end with a pin 86 which rides in the groove '78 on the forward end of the valve stem 75. ciated from the illustration in Fig. 5 that when the lever 79 is brought into ihe position as shown in full line, the wheel slide will be fed in a forward direction.

When the operator desires to move the grinding wheel slide rearwardly, the lever '79 is shifted It will be readily appre-' manually into position 7911 which rocks the lever 84 in a clockwise direction (Fig. 5) and thereby shifts the valve stem 75 so that the valve pistons assume the dotted line position, as indicated in Fig. 3. In this position of the valve stem 75, fluid enters through the port 45 into chamber 46'and passes through the port 60, pipe 59, passage 58, port 57, into the cylinder chamber 56, to cause a rearward feeding movement of the grinding wheel. I

It is desirable that a mechanism be provided for limiting the rearward movement of the wheel slide so as to avoid the necessity of the piston moving to its extreme rearward position. To accomplish this result, the piston rod 32 is provided with a rearwardly extending rod 88. A cam 89 is mounted on the rear end of the rod 88 and is arranged to engage an adjustable pin '90 which is adjustably supported in an elongated slot 91 in a lever 92. The lever 92 is pivoted on a stud 93 fixed to the bracket 94 on the base 13. The lower end of the lever 92 is connected by a pin 95 with a rod 96 which is in turn connected by a pin 97 to a bracket 98 which is slidably mounted on the valve stem 75. A collar 99, which is pinnedto the valve siem 75, limits the movement of the bracket 98 towards the rear and a spring 100 interposed between the bracket 98 and the turnbuckle 76 holds the bracket in'engagement with the collar 99.

It will be readily appreciated from this construction that when the lever 79 is moved into position 79a to start a rearward movement of the wheel slide, the cam 89 is in the position illustrated in Fig. 5 and the pin 90 is in the position 90a, as shown in broken line in Fig. 5. As the piston 31 moves rearwardly, the cam 89 engages the pin 90 and rocks the lever 92 in a counter clockwise direction (Figs. 4 and 5) to move the rod 96 and valve stem 75towards the front of the machine so as to shift the valve pistons 47 and 48 to cover the ports and 49 respectively and thereby stop the rearward feeding movement of the grinding wheel. The pin 90 is adjustably supported in the elongated slot 91 so that the time of movement of the valvc stem may be varied.

The hydraulic mechanism may be used merely for producing a rapid approaching and receding movement of the grinding wheel, and the grinding feed obtained by manual rotation of the cross feed screw while the piston is held against endwise movement. For certain types of grinding, however, it may be desirable to provide a suitable control for the wheel feeding mechanism so that the fluid pressure mechanism may control the feeding stroke of the grinding wheel and the manual rotation of the cross feed screw utilized merely to adjust the position of the wheel relative to the hydraulic piston in setting up the machine for a given operation. To control the hydraulic feeding movement of the wheel slide, it is desirable to provide a suitable automatically actuated control mechanism for the throttle valve 65 so that the wheel may approach the work at a rapid rate, then the speed be automatically reduced to a slower but uniform rate for grinding a portion of thework, then a still slower speed for'grinding the body of the work and finally a stopping of the wheel feed when the stop on the piston engages the end surface of the cylinder. The valve 65 is normally held biased to a closed position by means of a spring 105 interposed between the end of the valve casing and a turnbuckle 106. In order to attain a rapid approaching movement of the grinding the grinding wheel. As the piston moves forwardly to move the wheel rapidly into the work, the cam 89 strikes an adjustable screw 109 which is mounted on a slide 110 adjustably positioned on the upper end of a lever 111 which is pivoted on the stud 93. The lower end of the lever 111 carries an adjustable screw 112 which is arranged to engage a surface 113 on a trip block 114. The pawl 108 is preferably slidably keyed by means of a key 115 in an aperture 116 in the block 114. The block 114 is pivotally supported on a shaft 117 which is fixedly mounted to the brackets 118 on the base of the machine. A bushing 119 surrounds the projecting stud 120 which is formed as an integral part of the pawl 108. The bushing 119 is positioned in a notch 121 in the shaft 117 and engages a shoulder 122 which limits its movement towards the left, as viewed in Fig. 8. The left-hand end of the stud 120 (Fig. 8) is provided with a screw thread having an adjusting nut 123 which serves to position the pawl 108 relative to the stud 117 and thereby vary the position of the valve as desired A spring 124 surrounds the stud 1'20 and is interposed between the bushing 119 and the end of the pawl 108 and serves to hold the pawl 108 and the block 114 normally in the position as indicated in Fig. 8.

When the wheel slide andpiston 31 ,move forwardly, the cam 89 strikes the screw 109 and rocks the lever 111 about the stud 93 and moves the screw 112 downwardly, rocking the block 114 in a clockwise direction (Figs. 4 and 5) to rock the pawl 108 downwardly out of engagement with the latch 107. The released tension of the spring 105 then moves the valve stem 66 towards the right, as viewed in Figs. 4, 5, and 8. This movement continues until the latch 107 engages a second pawl 125. The stop pawl 125 is mounted in a block 126 which is pivotally mounted on the shaft 117. The pawl 125 is provided with a stud 127 projecting at the rear and provided with an adjusting nut 128. The other details of construction of the support for the pawl 125 are identical with the support for the pawl 108 and consequently, only one of these pawls has been shown in detail. The grinding wheel continues to move towards the work at a speed governed by the position of the pawl 125 which holds the throttle valve 65 in a' partially open position. Continued forward movement of the wheel moves the cam 89 to cause a further swinging movement of the screw 109 and lever 111 until an ad- .justing screw 129 engages a surface 113 on the nism that the final position of the grinding wheel is determined by the stop collar 53 engaging the end surface 54 of the cylinder 30. When the mechanism is operated in this manner, it is desirable that the fluid pressure be retained back of the piston so as to hold the stop collar 53 in rigid engagement with the surface 54'at the end of the cylinder to determine the final position when the work has reached a predetermined size. By adjusting the screw 131, the final position of the throttle valve may be controlled to produce the desired pressure back of the piston or, if desired, the screw 131 may be so adjusted that when the pawl 125 is tripped to release the latch 107, the valve will be entirely closed to allow no fluid to exhaust from the chamber 56.

When the hydraulic control of the wheel movement is utilized for a grinding feed, it is desirable to provide a simple mechanism for returning the throttle valve 65 to its initial or cocked position with the pawl 108 engaging the latch 107. In the preferred construction, a link 132 is fixedly mounted on valve stem between the end of the turnbuckle 76 and a look nut 133. The other end of the link 132 is slidably supported on the rod 130. When the operator moves the lever 79 into position 790. to shift the rod 77 and valve stem 75 rearwardly to cause a rearward movement of the grinding wheel, the link 132 is carried thereby and slides idly over the rod 130 until it engages a nut 134 and thereafter continued movement of the link 132 moves the rod 130 and valve stem 66 rearwardly to return the valve to its initial or cocked position with the pawl 108 engaging the latch member 107.

To attain a further object of this invention, namely, to provide a suitable truing speed for truing the side faces of the grinding wheel, it is desirable to have a slow but uniform speed of the wheel slide to produce the desired finish. To accomplish this result, a suitable positioning device is provided so that the valve may be positioned both on forward and reverse strokes to attain a very slow but uniform feeding movement of the wheel. This is preferably accomplished by providing the reverse valve 44 with the V-shaped ports 49 and 60. By utilizing the V-shaped ports 49 and 60 and positioning the valve pistons 47 and 48 in proper relation therewith, the desired slow truing speed may be attained. ,In order to permit accurately positioning the valve pistons 47 and 48 to attain the desired truing speed, a suitable mechanism is provided to limit the swinging movement of the control lever. The lever 84 is provided with an inwardly extending arm 135 which pivotally supports a U-shaped bracket 136 on a stud 137. Arms 138 and 140 of the U-shaped member 136 are provided with adjustable stop screws 139 and 141 respectively. During the normal operation of the machine, the U-shaped member 136 is swung into the broken line position 13611, as indicated in Figs. 5 and 9. When it is desired to true the grinding wheel on its side faces, the U-shaped bracket 136 is swung into the full line position, as indicated in Fig. 9,-so that the stop screw 139 is in the path of the-bracket 145 and the stop screw 141 is in the path of the lower surface of the arm 145. In this position of the parts, it will be readily apparent that the stop screw 139 engaging the arm 145 limits the movement of the valve stem 75 in one direction, while the screw 141 limits the movement of the valve in the opposite direction so that a slow movement of the grinding wheel slide may be obtained in either direction. By adjusting the position of the screws 139 and 141 relative to the U- shaped member 36, the position of the valve pistons 47 and 48 may be varied so that the desired speeds for truing either on the forward or reversed movement of the wheel may be obtained. A spring-pressed ball 148 is provided on the base 13 and arranged to engage a notch 149 in the arm 135 of the lever 84 to permit the operator to readily swing the lever 84 so as to position the valve 44 in a neutral position.

The operation of this mechanism is readily apparent from the foregoing disclosure. If it is desired to utilize the hydraulic mechanism merely as a positioning movement, then the operator merely adjusts the pawls 108 and 125 so that the throttle valve remains wide open. The operator may then cause a forward positioning movement of the wheel by moving the control lever forward into the full line position, as indicated in Fig. 5, allowing fluid to pass through the reverse valve into cylinder chamber 52 to move the parts into the position illustrated in Figs. 1, 2 and 5. Simi-v larly, when a rearward positioning movement is desired, the operator moves the lever 79 from the full line position, as indicated in Fig. 5, into the dotted position 79a, thereby reversing the valve 44 and admitting fluid to the cylinder chamber 56 to cause a rearward movement of the grinding wheel. When the wheel is positioned at the forward end of the stroke, the stop collar 53 engages the end surface 54 of the cylinder 30 and is held there by fluid pressure in the cylinder chamber 52. The operator may then by manual manipulation of the feed wheel 26 rotate the feed screw and cause a grinding feed of the wheel.

If desired to utilize a hydraulic feed throughout, then the stop pawls 108 and 125 are adjusted so that the pawl 108 engages the latch 107 to restrict the position of the throttle valve 65 for the initial feeding movement. As the grinding wheel feeds in a forward direction, the wheel approaches the work rapidly until the cam 89 pushes downwardly on the stop screw 109, rocking the lever 111 to move the screw 112 downwardly, thereby moving the pawl 108 downwardly out of engagement with the latch 107, allowing the released tension of the spring 105 to move the valve until the latch 107 engages the pawl 125 which produces a slower but uniform feeding movement of the grinding wheel. This movement may be for rough grinding the piece of work, which movement continues until the cam 89 moves the stop screw 109 until the screw 129 rocks the block 126 and moves the pawl 125 out of engagement with the latch 107 and allows the released tension of the valve spring 105 to further close the valve until the extension 130 of the valve stem 66 engages the stop screw 131 which determines the final position of the throttle valve. The grinding at this speed continues until the stop collar 53 strikes the end surface 54 of the cylinder 30, thereby limiting the infeeding movement of the grinding wheel.

In case it is desired to operate the feed mechanism in the latter described manner, the manual rotation of the cross feed screw 16 is utilized merely as a compensating mechanism to adjust for wheel wear and to retain the wheel in proper position for accurately sizing the work. The wheel remains in its forward position after the work has been ground down to size until the operator moves the lever 79 into position 79a to reverse the direction of flow of fluid and to admit fluid into the cylinder chamber 56 to cause a rapid rearward movement of the grinding wheel slide. The rapid movement; continues until the cam 89 strokes the screw 90 on the lever 92 and rocks the lever about its pivot 93 to swing the rod 96 and bracket 98 towards the right, as viewed in Fig.5, to move the valve stem so that the pistons 47 and 48 close the ports 49 and 60 to stop the rearward feeding movement of the grinding wheel.

Having thus described this invention, what is claimed as new and desired to secure by Letters Patent is:

1. A grinding machine comprising a base, a rotatable grinding wheel, a transversely movable slide therefor, a feed screw operatively connected to the slide and rotatable to efiect a grinding feed, a fluid pressure mechanism including a cylinder fixed to the base, a piston therein having a piston rod and an anti-friction bearing operatively connecting said piston rod to the feed screw for moving the slide endwise to position the wheel for grinding which is arranged so that the screw may be rotated without transmitting rotary motion to the piston.

2. A grinding machine comprising a base, roatable grinding wheel, a transversely movable slide therefor, a feed screw operatively connected to the slide and rotatable to effect a grinding feed, a fluid pressure mechanism including a cylinder fixed to the base, a piston therein having a piston rod, a key to prevent rotation of the piston, and an anti-friction bearing operatively connecting said piston rod to the feed screw for moving the slide endwise to position the wheel for grinding which is arranged so that the screw may be rotated without transmitting rotary motion to the piston.

3. A grinding machine comprising a base, a rotatable grinding wheeba transversely movable slide therefor, a feed screw operatively connected to the slide and rotatable to effect a grinding feed, a fluid pressure mechanism including a cylinder fixed to the base, a non-rotatable piston therein having a piston rod, an anti-friction bearing operatively connecting the piston rod to said feed screw for moving the slide endwise to position the wheel for grinding, a valve for said mechanism, a stop member on said piston rod arranged to engage the end of said cylinder and arrest the endwise movement of the screw, and a valve controlling device actuated by movement of said piston to throttle said valve when the movement of said screw is arrested, said. part being so arranged that said valve remains partially open so that fluid pressure retains said screw in an arrested position during grinding.

4. A grinding machine comprising a work support, a wheel slide, a rotatable grinding wheel thereon, a rotatable feed screw operatively connected to move the slide, a fluid pressure system operatively connected to said screw for moving and permit a partial closing of said valve to produce a slower but predetermined uniform feed of the grinding wheel.

5. A grinding machine comprising a work support, a wheel slide, a rotatable grinding wheel thereon, a rotatable feed screw operatively com nected to move the slide, a fluid pressure mechanism operatively connected to said screw for moving the screw endwise to feed the slide and grinding wheel towards and from the work to grind the same to a predetermined size including a throttle valve arranged to control the exhaust of fluid pressure mechanism, means to hold said valve normally biased to a closed position, a plurality of adjustable stops arranged to locate said valve in any one of a series of predetermined positions and means actuated by movement of said slide to move said stop to an inoperative position to permit a partial closing of the valve to reduce the feed of the grinding wheel to a slower but predetermined uniform feed.

6. A grinding machine comprising a work support, a wheel slide, a rotatable grinding wheel thereon, a rotatable feed screw operatively connecttd to move the slide, a fluid pressure piston and cylinder connected to said feed screw for moving the screw endwise to feed the grinding wheel towards and from the work, a fluid pressure system including a reversing valve for conveying fluid to either end of said cylinder, a throttle valve to control the exhaust of fluid from one, end of said cylinder and control the infeed of the grinding wheel, and means operated in timed relation with the wheel feeding movement to actuate said throttle valve and produce first a rapid approach of the grinding wheel towards the work axis, then a slower but uniform feed of the wheel to rough grind the work and finally to stop the infeed of the wheel.

7. A grinding machine comprising a work support, a wheel slide, a rotatable grinding wheel on said slide, a rotatable feed screw operatively connected to move the slide, a fluid pressure mechanism connected to said screw for moving the screw endwise to feed the grinding wheel towards the work axis, a fluid pressure system including a valve to conduct fluid to said mechanism and cause a rapid approach of the grinding wheel towards the work axis, a plurality of members operated in timed relation with the wheel movement to actuate said valve, the first, to produce a slower but uniform feed to rough grind the Work, the second, to produce a still slower but uniform feed to finish grind the work, and an adjustable stop to limit the infeed the grinding wheel.

8. A cylindrical grinding machine comprising a work support, a rotatable grinding wheel, a slide therefor, a fluid pressure system including a cylinder and piston for moving the slide, a reversing valve to admit fluid under pressure to either end of said cylinder to cause either a forward or rearward movement of said grinding wheel, a throttle valve which is biased to a closed position in the exhaust side of said system, a plurality of stops arranged to-hold said throttle valve in one of several predetermined positions, means actuated by the movement of said slide to trip one of said stops to partially close said throttle valve when the slide has reached a predetermined position, manually operable means for shifting the reverse valve to initiate either a forward or rearward movement of the grinding wheel, and connections between said manual means and throttle valve which are so arranged as to cock the latter in its initial position when the manual means is shifted to cause a rearward feed.

9. A cylindrical grinding machine .comprising a work support, a rotatable grinding wheel, a slide therefor, a fluid pressure system including a piston and cylinder for moving the slide, a reversing valve to admit fluid under pressure to either end of said cylinder to cause either a forward or rearward movement of said grinding wheel, a throttle valve which is biased to a closed position, a stop arranged to hold the valve in a predetermined position, means actuated by movement of the slide to trip said stop to partially close the throttle valve when the slide reaches a predetermined position, means actuated by movement of the slide to shift the reversing valve to cause a rearward movement of the grinding wheel, and means actuated by rearward movement of the wheel slide to move the reverse valve to a neutral position and to cock the throttle valve in its initial position when the slide reaches a predetermined position in its rearward movement.

10. A cylindrical grinding machine comprising a work support, a rotatable grinding wheel, a slide therefor, a fluid pressure system including a cylinder and piston for moving the slide, a reversing valve to admit fluid under pressure to either end of said cylinder to cause either a forward or rearward movement of said grinding wheel, a throttle valve which is biased to a closed position in the exhaust side of said system, a plurality of stops arranged to hold said throttle valve in one of several predetermined positions, means actuated by the movement of said slide to trip one of said stops to partially close said throttle valve when the slide has reached a predetermined position, manually operable means for shifting the reverse valve to initiate either a forward or rearward movement of the grinding wheel, and connections between said reversing and throttling valves which are so arranged as to cock the latter in its initial position when the former is shifted to cause a rearward feeding movement of the wheel.

11. A grinding machine comprising a base, a support for rotatable work, a rotatable grinding wheel, a slide to support said wheel, a nut depending from said slide,. a feed screw engaging said nut and supported for a rotary and axial movement on said base, manually operable means to rotate said screw and adjust the position of said wheel, a fluid pressure system including a cylinder and piston in said base and arranged in axial alignment with said screw, a reversing valve to admit fluid to either end of said cylinder to move said screw axially in either direction to cause a rapid movement of the grinding wheel, a throttle valve to throttle the exhaust of fluid from said cylinder which is normally biased to a closed posia reversing valve having ports arranged to admit fluid under pressure to either end of said cylinder, means for shifting the reversing valve to initiate either a forward or rearward movement of the grinding wheel, and a stop device to adjustably limit the movement of said reverse valve in either direction to allow only a partial opening of the ports to produce a slow forward and rearward movement of the grinding wheel.

13. A cylindrical grinding machine comprising a base, a work support, a rotatable grinding wheel, a wheel slide therefor, a fluid pressure system including a cylinder and piston for moving the slide,

a reversing valve having ports arranged to admit,

fluid under pressure to either end of said cylinder, manually operable lever for shifting the reverse valve to initiate either a rapid forward or rearward positioning movement of the grinding wheel, and a normally inoperative stop device which is movable to an operative position to adjustably limit the movement of said lever and valve in one direction to allow only a partial opening of said ports to produce a slow movement of the grinding wheel for truing thhe side faces thereof.

14. A cylindrical grinding machine comprising a base, a work support, a rotatable grinding wheel, a wheel slide therefor, a fluid pressure system including a cylinder and piston for moving the slide,

a reversing valve having ports arranged to admit fluid under pressure to either end of said cylinder, manually operable lever for shifting the reverse valve to initiate either a forward or rearward movement of the grinding wheel, and a normally inoperative stop device to adjustably limit the movement of said lever and valve in either direction to allow only a partial opening of said ports to produce a slow forward or rearward movement of the grinding wheel.

HERBERT A. SILVEN. 

